10a: vir-cell interaction Flashcards
Types of Virus-cell interactions:
struggle for life:
- resistance
- interferon production
- latency
- persistent infection
- oncogenicity
- Cytopathic effect (CPE)
What is ment by Abortive infection and Productive infection in Virus-cell interactions?
- Abortive infection: no virus release
- Productive infection: virus release and shedding
What are Interferon (IFN)?
IFN: cell-coded mediator protein - cellular defence mechanism
What are Interferon inducer?
dsRNA, RI forms –> cascade - IFN release
What are the IFN effects?
occurs: on the neighbouring cell
- structural changes on the cytoplasmic membrane -> decrease in penetration
- L-RNAse: mRNA degradation
- Proteinkinase: protein production inhibited
What are the different IFN types?
- IFN-alpha (epithel, leucocytes)
- IFN-beta (fribroblast)
- IFN-gamma (lymphocyte)
What is special about the IFN-alpha and IFN-beta types?
- heat and pH resistance
- viral induction
What is special about the IFN-gamma type?
antigen, mitogen induces
Is the IFN virus/host specific?
- not virus specific
- host specificity (bovIFN, hulFN)
What are the problems in therapy of IFN?
- expensive
- parental use, short-term efficacy
- the inducers (poly-inozine, poly-cytidine) are toxic
- toxic side effect
Latency
- after infection the virus does not multiplicate -> balance with the cell
- only the nucleic acid and eary proteins are present
- no virus shedding, no clinical sign, but carrier!
Types of viruses that show latency:
- Episoma (Papilloma-, Herpesviridae)
- Integration - provirus (Retro-, Polymaviridae)
Persistent infection:
- virus production, but no severe cell damage –> continuous shedding
Types of viruses that shows Persistent infection:
Flavi-, Retro-, Paramyxo-, Papillomaviridae
Oncogenic effect:
- cell proliferation
- less differentiated cell forms (“ancient”)
- less effective cell forms
- usually not able to function effectively –> tumors
Oncogenic DNA-viruses:
Papilloma-, Polyoma-, Adeni-, Herpes-, Pox-, Hepadnaviridae
Oncogenic RNA-viruses:
Retroviridae
Types of tumors:
- Benignant
- Malignant
What is typical for the Benignant type of tumor?
limited, less invasive, less destructive
What is typical for the Malignant type of tumor?
Invasive, destructive
Mechanisms of viral oncogenesis:
- Activation of cellular oncogenesis
- Expression of viral oncogenesis
- Viral proteins with consequent oncogenic effect
Virus typical for activation of cellular oncogenesis?
Retroviridae (Avian leukosis virus, Feline leukosis virus)
Activation of cellular oncogenesis?
- DNA integration into the cellular genome
- Near by c-onc genes
- Retroviral LTR regions –> intensive promoter - translation.
- ->c-onc activated - oncoprotein expression - cell proliferation
- -> slow developing lymphatic tumors (leukemias)
viruses typical for expression of viral oncogenesis:
Retroviridae (Avian sarcoma virus, Feline sarcoma virus)
expression of viral oncogenesis:
- recombination between the cellular and proviral genome
- transposition of the c-onc gene into the virus genome –> v-onc!
- the oncogene is carried by the virion
- after infection quick oncoprotein production
- fast developing malignant tumors (sarcoma, carcinoma)
- the v-onc gene is not essential for the virus
- replacing essential genes (envelope protein gene)
- defective particles - envelope from leukosis viruses.
Viral proteins with consequent concogenic effect:
- oncogenic DNA viruses
- viral modulator proteins control the cell machinery
- inativation of cellular anti-oncogenic proteins
- inhibition of the apoptosis (Adenoviridae)
- usually benignant tumors
What happens in in vitro cell cultures?
malignant transformation
- contact inhibition is terminated: microtumors
